The use of airbags in cars and other passenger vehicles helps to reduce injuries and prevent death from the external collision, and also helps to limit passenger collisions with the inside of the car. Airbags were first introduced in passenger cars by Ford in 1971 to protect the driver and front passenger in frontal collisions. Since then, the number of airbags in modern cars has increased to 5 and in some cases even 9, covering a wide range of accident scenarios.
Generally, there are two types of side airbag systems employed in the car seats. One with airbag installed on the side of car seat in the form of a visible, discreet door and the other is embedded in the under the foam layer of the upholstery. The use of removable/additional car seat covers in recent years, has gained popularity for reasons such as aesthetic appeal and protection of the upholstery. These seat covers are installed over the car seat upholstery and allow for the flexibility to change when desired and washed repeatedly.
Several manufacturers have introduced removable car seat covers with a rupturable seam known as a ‘tear seam’ along edge of the side panel of the seat cover to allow the deployment of the integrated side airbag concealed in the upholstery of car seat. However, many of these removable seat cover designs with ‘tear seams’ have been identified as having reliability issues during airbag deployment, due to several technical and design deficiencies.
Removable seat covers designed for side airbags generally deploy by rupturing the tear seam. The tear seam within the removable car seat cover must not prevent the full deployment of the airbag. The airbag deployment is executed with an enormous force which is responsible for the seam tearing. Until date this mechanism has been adopted commercially in removable car seat cover designs. However, the behaviour of tear seams in removable car seat covers can be unpredictable. Several factors such as seat cover material, type of sewing thread used at the tear seam, length of the tear seam, placement of the tear seam, and the type of stitch, affect the behaviour of airbag deployment.
Various problems can impact seam tear performance such as;
(a) the occurrence of ballooning of the removable seat cover material prior to the failure of the seam. This increases the time taken for the airbag deployment and hence reduces the effectiveness of the airbags.
(b) the improper and unsafe deployment of the airbag due to minor faults present in the seat-cover material such as holes, tears, rips or snags, which cause the inappropriate and incomplete exit of the airbag.
It would therefore be advantageous to provide an alternative means in a removable car seat cover to facilitate reliable airbag deployment in a car seat having an integrated side airbag.
Laser technology has been used in the textile industry for cutting of fabrics; engraving designs on fabrics and carpets; fabric pre-treatment to enhance fixation of dyes or treating of polymers to improve adhesion properties; and etching of graphics patterns on to the face of a material. Other methods such as UV weakening, caustic soda treatments of fabrics, including weakened yarns within a knitted or woven structure in strategic locations by changing the yarn inputs during manufacture have also been explored.
The concept of applying laser to a fabric material for the alteration of physical properties, specifically to pre-weaken the tensile strength of the fabric, leather, or polymeric materials used as trim cover of an airbag has been documented. U.S. Pat. No. 7,100,941 (Riha et al.) refers to the use of laser cutting beam based on an optical system which focuses the laser beam on fabric to facilitate cutting in a predetermined pattern for strategic weakening of fabrics applied to trim panels in the interior of a car that cover the exit points for the airbags. This U.S. patent is therefore directed toward providing a weakened portion of fabric moulded to underlying moulded dashboard using laser technology. While it is suggested that the invention may also be integrated into the knee bolster area, the steering wheel hub, or other areas in the interior of the vehicle including, but not limited to seats, headliner, Philip trim door panels, quarter panels, and roof rails, reference is not specifically made to seat covers subsequently applied as extra trim over the upholstery of a seat.
U.S. Pat. No. 6,140,602 (Costin), describes the application of laser beam to impart patterned designs on thin fabric and leather using an electronic controller to provide a signal to the drive mechanism for controlling the speed of etching.
U.S. Pat. No. 6,294,124 (Bauer et al.) discloses the use of controlled laser beam to weaken the back of the cover layer by cutting through the substrate and partially through the cover layer to produce grooves of a precise depth and width.
The concept of using laser to pre-weaken the tensile strength of fabrics is therefore not new, and as discussed above, can be used to impart cosmetic appeal and in some cases functional attributes such as facilitate airbag deployment. However there still exists the need for the development and demonstration of pre-weakening of fabrics to allow for reliable, predictable and timely deployment of airbags through the tearing of fabric. While many of such patents have attempted to modify fabric surfaces using laser to allow for deployment, the concept of pre-determined zone of known bursting strength of fabric to allow for reliable, predictable and timely deployment of airbags through the pre-weakened fabric has not been demonstrated.
In addition, there are several challenges that can be encountered when using the pre-weakening concept on removable car seat covers. Removable car seat covers unlike fixed trims and face fabrics that are adhered to the foam of the car seat (as in the case of OEM car seats) can distort and result in misalignment from the actual deployment zone. This is a serious performance issue and therefore warrants the need for development of a pre-weakened predetermined zone with of a known bursting strength in close proximation to the airbag exit point.
It is therefore an object of the present invention to provide a removable car seat cover, and a method of producing a removable car seat cover having a predetermined pre-weakened failure zone of known bursting strength for facilitating reliable side airbag deployment from a car seat.